The free-living nematode Caenorhabditis elegans will be used as a model system for the study of the genetic control of eucaryotic development. Embryogenesis will be analyzed by direct observations of cell lineages during normal and mutationally altered development in order to elucidate the basic rules that govern embryogenesis. One embryonic cell lineage will be studied in detail morphologically and biochemically. Cells of the specific lineage will be isolated and their mRNA and DNa compared to the mRNA and DNa from other lineages using recombinant DNA techniques in order to detect lineage specific gene expression or DNA rearrangements. Spermatogenesis will also be analyzed morphologically and genetically as a differentiation pathway. Existing maternal effect mutants will be further studied genetically and biochemically in order to understand the contributions of maternal genome expression to early development. Microinjection methods will be developed in order to assay maternal effect mutants by rescue with wild type cytoplasm. Attempts will be made to develop a generalized DNA transformation system for C. elegans in order to transfer and to isolate genes essential for development.